The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
(1) Field of the Invention
This invention generally relates to a rugged broad band underwater acoustic transducer element for conformal array applications.
More particularly, the invention relates to a shaped 1-3 piezocomposite sensor.
(2) Description of the Prior Art
Currently there is a need for broadband conformal acoustic arrays for various SONAR applications.
The following patents, for example, disclose piezoelectric transducer elements, but do not disclose a conformal application of piezoelectric composite transducer elements, or the conformal arrays of the same.
U.S. Pat. No. 5,950,291 to Gentilman et al.;
U.S. Pat. No. 5,964,175 to Sirmalis et al.;
U.S. Pat. No. 6,255,761 to Benjamin;
U.S. Pat. No. 6,232,702 to Newnham et al.; and
U.S. patent application Ser. No. 09/968,396 to Benjamin.
Specifically, the patent to Gentilman et al. discloses methods for fabricating a conformable composite acoustic transducer panel including a conformable composite-body having upper and lower planar faces and upper and lower thin, flexible electrodes bonded to the upper and lower faces, respectively. The composite body includes an array of individual piezoelectric or electrostrictive ceramic elements extending normal to the upper and lower faces and through the composite body from the upper face to the lower face to electrically contact the electrodes. Stiff integral faceplates are bonded to the side surfaces of the elements at their upper and lower ends. Alternatively, a conformable, stiff, voided polymer matrix is bonded to the element sides over their entire length. Flexible circuit boards may be bonded to the electrodes to provide electrical contact thereto.
The patent to Sirmalis et al. discloses a system for attaching one or more unmanned, hydrodynamically shaped, autonomous, undersea platforms to the bow of a submarine. An array of depressions, each matching the shape of the platforms, is provided in the bow of the submarine, equally spaced about the circumference of the submarine. Once seated in the depressions and attached to the submarine, the platforms provide a smooth, hydrodynamic shape to the bow of the submarine. Additionally, conformal arrays on the platforms mate with conformal arrays on the bow of the submarine to form a continuous conformal array and the platforms"" weapons systems provide the submarine with forward deployed weapons when the platforms are attached. A platform is launched by detaching it from the submarine bow and raising the leading edge of the platform slightly into the water flow around the bow. Hydrodynamic forces lift the platform away from the submarine for an acoustically quiet launch.
Newnham et al. discloses an electroactive device including an electroactive ceramic annular substrate having a pair of opposed planar annular surfaces, a hollowed interior region and a thickness aspect. A first cap having a concave shape that extends into the hollowed interior region includes a rim portion, bounding the hollowed interior region, and joined to a first one of the planar surfaces. A second cap having a concave shape that extends into the hollowed interior region includes a rim portion, bounding the hollowed interior region, and joined to a second one of the planar surfaces. A potential measured across the ceramic substrate enables a field change in the ceramic substrate to be sensed, the field change caused by flexure of the ceramic substrate as a result of a pressure applied to the first and second caps.
U.S. Pat. No. 6,255,761 to Benjamin provides a piezoelectric composite transducer and method for making the same. A block of piezoelectric material has a common base and a plurality of uniform-length rods extending from the common base in a parallel spaced-apart fashion to define an array. A first surface region is defined at outboard ends of the rods and a side region is defined about the periphery of the array. Electric conductors extend through the side region, are routed parallel to the first surface region, and are then led substantially parallel to the rods to the first surface region. Spaces between the rods are filled up to the first surface region with a viscoeleastic material. The common base of the block is then removed such that a second surface region parallel and opposite the first surface region is defined. Electrodes are deposited at the first surface region to be in contact with the rods and in electrical contact with the electric conductors. A ground electrode is deposited at the second surface region to be in contact with the rods. The resulting piezoelectric composite transducer can be heated and shaped to conform to complex curves.
U.S. patent application Ser. No. 09/968,396 to Benjamin provides that an ultrasonic sparse imaging array includes a substrate of an acoustically absorptive material, through which extends a multiplicity of holes. Adhesive sheets, having selectively conductive regions, are fixed to a first side of the substrate, and are each disposed over a first end of one of the holes. Plano-convex shaped transducer elements, having a wide acoustic field of view, are disposed on each of the sheets, each of the sheets serving as a positive electrode and providing a mechanical and electrical connection between the substrate and a multiplicity of transducer elements. Plating is fixed to the first side of the substrate and covers each of the transducer elements and comprises a negative electrode. A conductive epoxy fills each of the holes and a power source is in electrical communication with the negative electrode.
It should be understood that the present invention would in fact enhance the functionality of the above patents by providing a transducer fabrication with conformal array applications that is low in cost and provides a wide bandwidth.
Therefore it is an object of this invention to provide a broadband transducer element.
Another object of this invention is to provide a broadband transducer element of a shaped piezoelectric polymer composite material.
Still another object of this invention is to provide a broadband transducer element of a shaped composite material and having multi-element sub-arrays.
A still further object of the invention is to provide a broadband transducer element of a shaped composite material in which the shape of the composite material conforms to a given geometry.
Yet another object of this invention is to provide a broadband transducer element having plural shaped composite elements.
In accordance with one aspect of this invention, there is provided a composite transducer having a formed substrate of a piezoelectric polymer composite material, the formed substrate including at least a first and second surface. Conductive electrodes are deposited on the first and second sides of the formed substrate. One side of the formed substrate is bonded to an acoustically absorptive backing material whereas the other side conforms to any given singly or double curved geometry.